[SOLVED] ESC wiring clarification

Navio / Edge Hardware
1

I am wanting a bit of clarification on the documentation on this page: http://docs.emlid.com/navio2/Navio-APM/hardware-setup/

In particular, the snippet:
“Only one ESC power wire (central) should be connected to Navio2 servo rail, otherwise BECs built in ESCs will heat each other.”
Out of each of my 4 ESCs I have a servo cable with 3 wires: Yellow, Red, Black. It looks like to me they are pulse, + and - respectively.
Is the documentation telling me that I should remove the Red (+) and Black (-) wires from all but ONE of my servo cables that plug in to my Navio?

Photo of said ESC servo cable here: https://drive.google.com/file/d/0B6dT7W9NhU2vbEtsZFVubVdua2M/view?usp=sharing

2

Yep, I’m also confused about exactly the same thing.

3

Although the “servo rail” doesn’t need power for the ESCs themselves, if you have RC input (strongly recommended) or any other devices that want power from ADC, RC or PWM/servo 1-13 connectors you will need to connect something with +5v there. But only one 5v input, hence the warning.

As it’s common for ESCs to have BECs this means you have 4 times 5v input (on a quadcopter, 8 on an octocopter) which cannot be connected together without special circuity to prevent overload. The BEC components will overheat each-other as documented.

Just disconnect all but one of the red wires from the ESCs and tape back or use directly for other purposes (as they have a common ground that is okay).

Personally I prefer to buy opto ESCs, which have no BEC, first to reduce interference and second to save a little weight. Then I buy a PDB with a 5v (and 12v when I want a live FPV transmitter) or install a separate BEC.

Also be aware of the amperage rating of the chosen ESC or BEC’s output. It will most likely be enough for Navio but if you hang a load of USB devices and WiFI dongles with the “max_usb_current” option you will need a separate BEC with a higher rating.

1 Like
4

I thought I would update this thread with my experience-

I connected my Radio Rx to the PPM input of the Navio. No problem. All working and with power.
I removed the Red + wires from all but one of the ESCs. Which I thought was the recommendation in the documentation.
As soon as I connected ESC #1 (the one with the + wire) the power to my Navio would drop out. But my ESCs were powered
I ended up removing the Red + wire from ESC #1 as well (so NONE of the Red + wires from ESCs were connected to Navio) and the power to my Navio stayed on and my ESCs were all powered. I have throttled up my drone successfully and all seems well.

The ESCs I am using are Multistar 20A Flashed with SimonK.

5

I have been flying my drone for a few weeks now with none of the red wires connected to the Navio as described in my previous post.

Now I have built a servo controlled gimbal and need to power 2 servos. I decided to connect back in the red wire from the ESC that powers my #4 motor. That is the only one I connected.

Unfortunately I have the problem described in my previous post- when I connect any one of the red wires from my ESCs my Navio does not power up.
Any suggestions about why this would be? And what I can do to power my servos? Ideally I don’t want to buy a BEC as my ESCs have BECs in them and I’d like to be able to utilise them

6

@Bradley_Scott Could you please measure the voltage on those red wires? Also, what is the current rating of BECs in your ESCs?

7

Ah. That identified my problem. Looks like my ESCs aren’t as advertised. They are passing through the entire voltage from my battery. The red wire voltage was nearly 12v

I guess my options are:

  • Buy a BEC and connect that in to my battery.
  • Swap out my ESCs with the ones I thought these ones were: Multistar 20A ESCs with 5v 4A BECs

Any other suggestions for how I could step down the voltage?

8

I think that separate 5V BEC should be the easiest solution here.